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Subject: [PATCH 3/4] SUNRPC: Per-rpc_clnt task PIDs
From:   Chuck Lever <chuck.lever@oracle.com>
To:     trondmy@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Date:   Mon, 04 Oct 2021 10:10:10 -0400
Message-ID: <163335661005.1225.6870220946398100360.stgit@morisot.1015granger.net>
In-Reply-To: <163335628674.1225.6965764965914263799.stgit@morisot.1015granger.net>
References: <163335628674.1225.6965764965914263799.stgit@morisot.1015granger.net>
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The current range of RPC task PIDs is 0..65535. That's not adequate
for distinguishing tasks across multiple rpc_clnts running high
throughput workloads.

To help relieve this situation and to reduce the bottleneck of
having a single atomic for assigning all RPC task PIDs, assign task
PIDs per rpc_clnt.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/clnt.h |    1 +
 net/sunrpc/sched.c          |   12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index bd22f14c4b19..d5860a000806 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -40,6 +40,7 @@ struct rpc_clnt {
 	int			cl_clid;	/* client id */
 	struct list_head	cl_clients;	/* Global list of clients */
 	struct list_head	cl_tasks;	/* List of tasks */
+	atomic_t		cl_pid;		/* task PID counter */
 	spinlock_t		cl_lock;	/* spinlock */
 	struct rpc_xprt __rcu *	cl_xprt;	/* transport */
 	const struct rpc_procinfo *cl_procinfo;	/* procedure info */
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index c045f63d11fa..b3402aeb8f30 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -277,9 +277,17 @@ static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
 static void rpc_task_set_debuginfo(struct rpc_task *task)
 {
-	static atomic_t rpc_pid;
+	struct rpc_clnt *clnt = task->tk_client;
 
-	task->tk_pid = atomic_inc_return(&rpc_pid);
+	/* Might be a task carrying a reverse-direction operation */
+	if (!clnt) {
+		static atomic_t rpc_pid;
+
+		task->tk_pid = atomic_inc_return(&rpc_pid);
+		return;
+	}
+
+	task->tk_pid = atomic_inc_return(&clnt->cl_pid);
 }
 #else
 static inline void rpc_task_set_debuginfo(struct rpc_task *task)